| 摘要 |
PURPOSE:To transmit a sound signal for a call with inexpensive constitution by providing a switching means for connecting selectively a transmission line to one of a transmitting and receiving circuit of each device and a telephone set, on a master station device and slave station device, switching this switching means at every prescribed time limit only in a state that the telephone set is useable, and transmitting the sound signal and a data signal in a time division mode. CONSTITUTION:When a switching relay 10 is operated by off-hook of a transmitter- receiver of a telephone set 7, its contact 10AB is connected to the side of the telephone set 7, and the telephone set 7 is connected to a line 3. As a result, communication of the telephone set 7 can be executed. However, when an operation time of a timer 13 elapses, its normally closing contact 13B is opened and the switching relay 10 becomes off. On the other hand, a normally opening contact 13A of the timer 13 is opened and a transmission available pulse OK of a transmitting circuit 8 becomes 'H'. Thereafter, while a hook switch FS of the telephone set 7 is on, this operation is repeated, and a call sound signal (a call time is an operation time of the timer) and a data signal (a data transmission time of once is 1 second - 3 seconds) are sent out alternately.
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